Sorry for the slightly off-topic question, but does anyone have an idea to get Sky130 projects to interface with SDRAM (perhaps SDR?) memory?

Do you mean interfacing to external SDRAM chips? I don't think there are enough pins for that. Perhaps if you can accept an 8 bit data bus. In that case you can simply include the Verilog for some SDRAM controller (there are several available, though many are pretty bad - don't handle block transfers, for example) from the Internet in your project. If you mean using OpenRAM to implement an on chip SDRAM then sky130 doesn't have the capacitors needed.