Give each product a price value. Since it's early childhood, regular prices wouldn't be appropriate. Give different products different whole numbers like $2, $5, etc. Create math problems by having them go grocery shopping and add up the amount. You could even have them do subtraction problems by "paying" for the items (I have $10 and bought $7 worth of groceries- how much will I have left?).
For a writing activity, post a picture of a grocery store on the board. Have students raise their hands to identify different things they see and write down their answers on the board (drawing a line from the item to the word). This is a great activity for ELLs. You can then use the words they list to create simple writing sentences (or dictate as you see fit), focusing on descriptive words. We use this in upper elementary grades to help students brainstorm words and ideas for writing prompts.
For drama, students can pretend to be the cashier and customer and perform skits on grocery store etiquette and safety (which gets a little into the health aspect).
In my state, one science objective for kindergarten is to "make observations and build an understanding of the properties of common objects." This can be done to describe the different foods and products you can buy at the grocery store. Measurement is also part of the kindergarten curriculum. Students could choose from various objects to measure different items at the grocery store (measure the length of a Mac and Cheese box using paper clips, etc.). In first grade that first objective is expanded upon when a student should "make observations and conduct investigations to build an understanding of the properties and relationship of objects." Students can compare like and unlike things using shape, color, texture, and size. Oooh! And for math you could graph stuff. Kids love to graph, especially when candy is involved.