If you want a string output, just combine the previously mentioned serialization with base64 encoding.
julia> using Serialization, Base64
julia> test = base64encode(serialize, (a="Hello World",b=2))
"N0pMBwQAAAA0EAEKTmFtZWRUdXBsZR9OAQRNYWlum0QCAAAAFAJmZxBTH04BBE1haW6bRAIAAAAAIQAIIQtIZWxsbyBXb3JsZOE="
julia> deserialize(IOBuffer(base64decode(test)))
(a = "Hello World", b = 2)
Just be aware that the serialization format isn’t designed for long-term storage (i.e, it might change in the future, though probably not any time soon). Also, there are potential security issues, for example Document security properties of Serialization · Issue #32601 · JuliaLang/julia · GitHub (but this is also a problem for JLD2: Security issue: Type confusion, convert called during deserialization · Issue #117 · JuliaIO/JLD2.jl · GitHub).