In tested the hypothesis that Dönner is larger when visiting a place where I tipped before and measured 10%-15% increase in weight ( 5 places, 3 Döner each, weight difference between fist and third).
But still, do not promote tiping culture. It sucks.
There is so many ways the quality of what you get can be modified:
Is the meat fresh from the spit or is it already cut off at the plate below or even in the little box at the side ?
Do you get the tomato slices from the from or the back?
Hot sauce from the shelf or from the side stash?
The funny thing is, it really only works if the tip makes you stand out positively.
So, yes please don’t tip, so my little hack keeps working.
Disclosure: I had the displeasure of being forced to work at a kebab Imbiss.
If the sign says one price, the cashier says a second, and the cash register says a third? You've found the best kebab in town.
No. Tipping is bullshit and you won't convince me otherwise. When I go a restaurant I want to have a nice experience, not deal with a pushy waiter begging me for a tip like a Syrian refugee begging for a coin because he hasn't eaten in days. "But if I tip I get a bigger kebab" yes, and you ruin the experience for everyone else because you teach service providers that displaying one price but actually charging another is a good business practice. If you want a bigger kebab, why don't you just pick it from the menu?
Tipping culture is horrible.