You can do this very directly:

list = {{195, 0.81}, {200, 0.33}, {205, 0.68}};
ExportString[list, "TSV"]
(* "195\t0.81\n200\t0.33\n205\t0.68\n" *)

If you want to trim that trailing newline,

StringTrim[ExportString[list, "TSV"]]

Another option:

StringRiffle[list, "\n", "\t"]

One way is to export to tsv format:

Export["~/Desktop/lst.tsv",
 {{195, 0.81}, {200, 0.33}, {205, 0.68}}]
Import["~/Desktop/lst.tsv", "Text"]// InputForm

You can also do it one step at a time:

{{195, 0.81}, {200, 0.33}, {205, 0.68}};
Map[ToString, %, {2}]
Map[Riffle[#, "\t"] &, %]
Riffle[%, "\n"]
% // Flatten
% // StringJoin // InputForm