You made me get up to look for a tape measure. Couldn't find one. 2e coin will have to do.

The Hellmans mayo bottle is definitely not 3cm. The other one is way wider but the Hellmans is barely the size of a 2e coin, a 2e coin not fitting in it and a 2e coin being roughly an inch (25.75cm as opposed to an inch which is 2.54cm)

Look at this

Idk of any inch wide mini spatulas. Could be useful but I've not seen any.

My ketchup bottles are also probably closer to 2" than 1"

Oh and I'm not gonna use the bottle I had the coin on, it was on sale but I didn't like it so I'm just waiting to throw it away. Also I don't ever scrape bottles of month old mayo, if I make my own I use it like at least within a week. Even if it's mixed from mayo and other premade sauces that have long shelf lifes. I just use the bottle as a sort of medium. I make a mix of sauces, because the ketchup isn't tasty enough, but the mayo ain't hot enough, and the mustard isn't sweet enough. So I mix a bit of all in decent relations, then throw in a bit of garlic, spices, jalapeño relish. Then blend and put in the squirter.

Use for a day or a couple. Then get rid.

Then rinse and repeat.