No special equipment or modifications are required. :)
I regularly use my dash to heat:Below are some Real World pictures, then some tips...
Left-to-right:
two bottles of water,
two cans of condensed chicken noodle soup,
5 cookies (from a mix package) on parchment paper,
MRE entree,
solar light:
Left-to-right:
two bottles of water,
one can of condensed chicken noodle soup,
bowl with precooked pasta (from a retort pouch)
with shredded cheese on top (covered with plastic wrap to keep bugs out):
Left-to-right:
solar stake light,
can of SpaghettiOs,
bottle of water,
can of soup,
precooked pasta retort pouch,
yet :) another can of SpaghettiOs:
When I relocate, usually I immediately put at least one bottle of hygiene water and my solar light on my dash.
For water heating, I usually use tall & narrow 500 mL "flavored" water bottles,
that are robust (same as soda bottles),
and their shape means they have a higher surface area to volume ratio
(theoretically this should improve heating, however I'm never in a rush so it hasn't been a factor for me).
I've also reused 2L soda bottles, which worked very well.
The main issue is the large soda bottles stand out more (so might be "unsightly" in an urban setting),
and hold far more water than I'd normally use (I'm clumsy and prefer to minimize issues with handling such large quantities of hot water).
Soup Pro Tip:
The small cans get very hot, and can be stressful to open,
due to the much greater risk of spilling (i.e. pressure buildup and difficulty holding).
I carefully crack the can open (to release pressure), gently pry it open to about a quarter to a half (whatever is easy),
then pour out as much as is easy.
Next, I open the top the rest of the way, without having to worry about spilling. :)