Its hot enough to chemically alter things, activate diffusions, speed bacterial growth, etc.
Its not hot enough to sterilize what you're ingesting.
(sadly before the era of camera phones, but the needle crystals really did look neat. The contents of the bottle were not ingested.)
Coke delivery guys make sure to rotate the diet soda when they deliver it (my wife took a day-in-the-life tour when she was at coke)
This sounds bad, but it's worth keeping in mind that plain tomato juice has something like 6x methanol in it than diet sodas. The quantities involved are tiny. Aspartame is metabolized in the same way when consumed cold. The big reason soda manufacturers are concerned about heat is that it loses its sweetness.
(all that being said, it's probably still a good idea to avoid anyway)
Its not ideal but even just keeping them in a small drink ice chest in a shaded/insulated area and keeping the van ventilated will help keep temps down.
Thoughts:
- You really need a cigarette lighter mini fridge. They're less than $100 at home depot. Note, they suck, but you don't have alternatives and you'll be able to have a cold beer occasionally.
Careful not to drain the car battery, and keep it in a shaded part of your vehicle.
- I find that there can large T differences in the car. Under the seat is fairly cool, and the T is more stable.
Keep your meds and the mini-fridge there, preferably by the floor vent if equipped.
- Does your van have windows or is it a workman's van? Glass is your enemy. You probably cant afford to just buy a van, but a white windowless Transit van is better than a Pacifica.
- Use white bed sheets to cover your interior and shade everything.
- you probably do this, but solar windshield covers.
- Keep your windows open a crack. Really just a crack small enough to keep even the rain out. Convection is huge. This is most important at day if crime is locally a problem.
- Paint it white.
- If you can, take advantage of the van's mobility and move to fairer weather throughout the year. If you have to stay in the LA region, go north just across the mesa (?) towards S. Barbara. Much cooler there. Id set myself up in Montecito myself.
A professional semi-chemist sounds much more interesting.