Runners absorb a completely training stress than the multisport athlete. Furthermore, the race day effort of a triathlete is based on the race distance, which determines what time of the day a triathlete runs and what type of mechanical fatigue the triathlete brings to the run. Thus, the pacing and fueling strategy for run training and running are very different than the single sport athlete.
(Note - even for runners, I still find it valuable to set up aid stations or bring nutrition and hydration with you during long runs)
For the triathletes, you can not think like a runner when you train for triathlons.
For example, if you are doing a brick run, you can not think of your run off the bike as "only" a 20-minute run. I see it all the time - a triathlete is out on his/her bike for 3, 4, 5+ hours and then comes the run off the bike and no fluids are consumed during the run. If you ride your bike for 3 hours and run 20 minutes off the bike, you are completing a 3 hour and 20 minute workout - you can not think that you are "only" running 20 minutes. Sure, a solo 20 minute run does not need calories or fluids but your body still requires and deserves fluids, electrolytes and calories to finish off your workout.
Once this new fueling strategy is ingrained into your head, you will notice that you are running better off the bike (not barely surviving or suffering), you are more energized and thinking clearly during a run off the bike, you are protecting your health (allowing you to train more consistently), you can reduce risk for injury and you can reduce your overall training stress, thus allowing you to recover faster. I can't tell you how many athletes that I have worked with who consistently underfuel and underhydrate while running all because it doesn't seem natural or needed to bring nutrition and hydration on a run. By fueling and hydrating properly, not only do you build confidence for race day, train your gut and improve performance but you protect your health AND you can function better in life (your family can thank me for this advice).
-If you are using a hydration beverage (ex. sport nutrition product that provides calories and sodium, which is recommended), you will reduce the risk of overdrinking on plain water, as it is typical for athletes who run without a sport drink to either overdrink on water when they stop or get to a water fountain/gas station or only consume water during a long run (or after a long bike) thus depleting sodium stores.
-If you prefer gels, use a gel flask (1 gel mixed in water in a small flask) for easy sipping. It's recommended to use a gel flask instead of consuming a gel every 45 minutes as a gel is properly digested and absorbed with 12-16 ounce of water. Using a gel flask dilutes the gel for easier digestion.
-Incorporate walk breaks into your run training regime to get more comfortable consuming fluids and calories when you are running. It can take up to 6 weeks to train your gut if you are not yet comfortable (or tolerating) consuming nutrition when you run.
(This is recommended for hot weather training).
Also, if you feel that your mouth gets tired of the "sweet" taste of a sport drink, have a sip of a carbonated drink, consume something sour or take a bit of a savory bar (ex. peanut butter, chocolate, bacon-flavored, etc.) to excite the taste buds so that you can return back to your routine fueling regime.