Before my Whole30, I was addicted to sugar in general, and Pepsi specifically. The best way I found to quit soda is to make sure I always have an attractive alternative in the fridge. For me, that is not water. I like water, but if there's soda in the fridge, I will always reach for that first. If you don't live with a soda drinker and can simply not have it in the house, that is great! That's not an option for me, so I have to distract myself with other beverages.

During the winter I drink a lot of coffee and tea. Stock up on some flavors you like so you'll always have fun options. During the summer I always have a big pitcher of iced tea in the fridge. Not just iced black tea, but iced mint and other light refreshing teas. I switch it up so I never get tired of them. You can try putting fruit in your teas while they steep to add some sweetness and flavor complexity.

My final line of defense (in case I'm lazy and don't want to make tea or coffee) is flavored seltzer water. It's a bubbly soda alternative with no sugar but a bit of yummy fruity flavor. This stuff is just carbonated water and natural flavors. It's cheap at the grocery store. Make sure you read the ingredients, because some brands put in unnecessary junk. I buy Polar brand, which just has those two ingredients.

Two thirds of the way through a marathon, many runners begin to complain of pain. My advice is usually to run faster!

As your glutes and hamstrings fatigue toward the end of a run, your ankle pronates more due to inward hip rotation which would overstress your posterior tibialis tendon which goes behind your medial ankle to the inside of your arch. The hamstring fatigue lengthens your slowing stride which makes things worse.
As your stride lengthens and you slow, you heel strike more and your foot tends to slap sown. In order to prevent toes from slapping you employ the toe extensors and anterior tibialis eccentrically. The toe extensors pass through synovial lined tendon sheaths for lubrication. The synovial sheaths can become inflamed and even swell.

If you run faster, you land flatter, so you should try speeding up about 10%. When you fatigue, you should walk until you can run fast with good form. When you are too tired to do that, you should just walk.
Running with poor form just trains poor form and fatigues you for the next training session, lengthening recovery time.

Running down hill causes more stress on the anterior tibialis and toe extensors as they try to slow your forefoot down at the increased angle. The answer is to lean slightly forward on your ankles and shorten your stride which will have your legs moving faster but less ankle angle.

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